This invention relates generally to magnetic disk data storage systems, and more particularly to the use of a ramp to facilitate the loading and unloading of sliders.
Magnetic disk drives are used to store and retrieve data for digital electronic apparatuses such as computers. In FIGS. 1A and 1B, a magnetic disk data storage system 10 of the prior art includes a sealed enclosure or housing 12, a spindle motor 14, a magnetic medium or disk 16, supported for rotation by a drive spindle S1 of the spindle motor 14, a voice-coil actuator 18 and a load beam 20 attached to an actuator spindle S2 of voice-coil actuator 18. A slider support system consists of a flexure 22 coupled at one end to the load beam 20, and at its other end to a slider 24. The slider 24, also commonly referred to as a head or a read/write head, typically includes an inductive write element with a sensor read element.
As the motor 14 rotates the magnetic disk 16, as indicated by the arrow R, an air bearing is formed under the slider 24 allowing it to xe2x80x9cflyxe2x80x9d above the magnetic disk 16. Discrete units of magnetic data, known as xe2x80x9cbits,xe2x80x9d are typically arranged sequentially in multiple concentric rings, or xe2x80x9ctracks,xe2x80x9d on the surface of the magnetic disk 16. Data can be written to and/or read from essentially any portion of the magnetic disk 16 as the voice-coil actuator 18 causes the slider 24 to pivot in a short arc, as indicated by the arrows P, over the surface of the spinning magnetic disk 16. The design and manufacture of magnetic disk data storage systems is well known to those skilled in the art.
Reducing the distance between the slider 24 and the spinning disk 16, commonly known as the xe2x80x9cfly height,xe2x80x9d is desirable in magnetic disk drive systems 10 as bringing the magnetic medium closer to the inductive write element and sensor read element improves signal strength and allows for increased areal densities. However, as the fly height is pushed to lower values, the effects of contamination at the head-disk interface become more pronounced. Specifically, debris may be collected over time on the air bearing surface of the slider 24 and which may ultimately cause the slider 24 to crash into the magnetic disk 16 causing the disk drive system 10 to fail. Consequently, reducing contamination within the sealed enclosure 12 is a continuing priority within the disk drive industry.
One strategy that has been used to reduce the debris that collects on slider 24 is to focus on the tribology at the head-disk interface to reduce the amount of contact between the slider 24 and the disk 16 when the system 10 is started and stopped. Traditionally, when a system 10 was shut down the slider 24 was parked on a track at the inner diameter (ID) of the disk 16 commonly known as a landing zone. There the slider 24 would rest in contact with the surface of the disk 16 until the disk was spun again, at which point the air bearing would form and the slider 24 would lift back off of the surface. Unfortunately, the friction and wear that occurred in these systems at the head-disk interface, even with improved lubricants, created unacceptable amounts of debris on the slider 24 to allow for still lower fly heights. In order to reduce friction and wear at the head-disk interface so as to reduce debris accumulation, the landing zone was improved by making it textured, often with a pattern of bumps, in order to reduce the contact area between the slider 24 and the disk 16, among other reasons.
Textured landing zones proved effective to a point; however, the need to fly the slider 24 still lower, with the inevitable need to reduce contamination further, led to the development of techniques whereby the slider 24 is held off of the surface of the disk 16 when not in use. Such techniques seek to avoid any contact between the slider 24 and disk 16 at all. However, simply lifting the slider 24 higher off of the surface of the disk 16 is not sufficient because a system 10 in a portable computer system is subject to shock that can cause the slider 24 to slap into the disk 16. Therefore, a technique used in the prior art to securely park the slider 24 away from the surface of the disk 16, as shown in FIG. 2, is to employ a small ramp 30 placed proximate to the outer diameter (OD) of the disk 16 and tab 32 attached to the slider 24. As the voice-coil actuator 18 causes the slider 24 to move toward the extreme OD the tab 32 rides up on the ramp 30 and lifts the slider 24 away from the surface. The slider 24 is pushed still further along the ramp 30 past the OD of the disk 16 to be parked on a flat or slightly indented portion on the ramp 30.
FIGS. 3 and 4 serve to better illustrate the relationships between the components of ramp systems of the prior art. FIG. 3 shows an elevational view, taken along the line 3xe2x80x943 in FIG. 2, of a slider 24 of the prior art suspended beneath a load beam 20 by a flexure 22. Attached to the end of the load beam 20 is a tab 32 intended to move in sliding contact with a ramp 30 for loading and unloading the slider 24. Although shown as attached to the end of the load beam 20, it should be noted that the tab 32 is typically formed as an integral part of the load beam 20.
FIG. 4 shows an elevational view, taken along the line 4xe2x80x944 of FIG. 2, of the ramp 30 relative to the tab 32, read slider 24, and the disk 16, when the slider 24 is flying and the tab 32 is disengaged from the ramp 30. For clarity, the load beam 20 and the flexure 22 are not shown. The tab 32 has a rounded bottom surface to reduce the contact area with the ramp 30 when the two are in sliding contact. Arrows in FIG. 4 indicate the directions of motion of the load beam 20 for both loading and unloading.
One problem with a ramp 30 of this design is that the tab 32 is in sliding contact with the ramp 30 each time the system 10 is started or stopped. The sliding contact produces wear contamination that can be transferred to the disk 16 to be picked up by the air bearing surface of the slider 24. The wear may be reduced by shaping the tab 32 so that the surface that contacts the ramp 30 is convex and by employing a lubricant. Although the amount of wear debris formed in this way is less significant compared to that which is generated with textured landing zones, nevertheless it may interfere with the aerodynamics of the slider 24 at very low fly heights and lead to crashes.
Another problem encountered with ramps 30 is that the slider 24 is not entirely parallel to the surface of the disk 16. Rather, the leading edge of the slider 24, the one facing into the direction of the rotation of the disk 16, is higher than the trailing edge of the slider 24 to provide lift. Viewed another way, the pitch on the slider 24 causes the trailing edge to be closer to the surface. Similarly, since the air flow under the side of the slider 24 nearest the OD is always greater than under the side nearest the ID, the slider 24 may have some roll such that the ID edge of the slider is lower than the OD edge. Consequently, the corner of the slider 24 on the ID side of the trailing edge is commonly closest to the surface. As a slider 24 is loaded over a disk 16 the tab 32 slides down the ramp 30 until the lift experienced by the slider 24 is sufficient to cause the slider to fly.
What is desired, therefore, is a way to park the slider 24 on a ramp 30 while minimizing as much as possible the wear between the tab 32 and the ramp 30. It is further desired to provide a smoother transition during loading and unloading.
The present invention provides for a ramp to assist the loading and unloading of a slider in a magnetic disk drive. The ramp comprises a body having a first surface and a second surface and a plurality of apertures extending between them, where each aperture has a first opening at the first surface and a second opening at the second surface. The first surface of the ramp further comprises a sloped segment and a straight segment, with the sloped segment being acutely angled with respect to the second surface. The ramp of the present invention directs a portion of a flow of air proximate to a spinning disk through the apertures in order to lift and cushion a tab attached to a load beam from which a slider is also suspended.
In a preferred embodiment of the present invention the air flow emerging through the first openings is sufficient to suspend the tab above the surface of the ramp. By maintaining an air bearing between the tab and the ramp while the slider is loaded and unloaded, wear and contamination from sliding contact can be greatly reduced. Another advantage realized by the present invention is that an air bearing can smooth the transition both as the tab leaves the ramp during loading of the slider, and as the tab re-engages the ramp during unloading.
In other embodiments the air flow emerging through the first openings is not sufficient to hold the tab completely off of the surface of the ramp. In still other embodiments the air flow emerging through the first openings is sufficient to hold the tab completely off of the surface of the ramp only over some length of the ramp such as the sloped segment. These embodiments still provide an advantage over the prior art in that any lift at all that is provided to the tab will tend to reduce the contact force between the ramp and the tab. Any reduction in the contact force will further tend to reduce wear and contamination from sliding contact. The lift provided to the tab in these embodiments, although not enough to suspend it completely off of the surface of the ramp, nevertheless can also smooth the transitions as the tab engages and disengages from the ramp.
Further embodiments of the ramp are directed at variations of the second surface. The second surface may be flat, but in some embodiments the second surface is non-planar and shaped to better urge a flow of air proximate to the surface of the disk into the plurality of apertures. For example, the second surface may be concave or may be provided with an aerodynamic shape. Shaping the second surface is advantageous to the present invention in that it provides a greater air flow into the plurality of apertures thus providing a greater lifting force against a tab situated above the first surface.
Still other embodiments are directed towards the apertures themselves. Each aperture has a first and second opening and in some embodiments their cross-sectional areas are substantially equal. In other embodiments the cross-sectional area of the first opening is less than the cross-sectional area of the second opening. In further embodiments the apertures are substantially straight, while in others they take complex paths through the body of the ramp. For example, an aperture may have an S-shape. Yet other embodiments are directed towards apertures that intersect the second surface at an angle to a tangent of the second surface at the location of the aperture""s second opening. Still more embodiments are directed to apertures that branch within the body of the ramp such that a second opening may connect to more than one first opening. Yet other embodiments are directed to apertures having nozzles formed at their first openings. Finally, some embodiments are directed to the cross-sectional shapes of the first and second openings and to the arrangements of the openings on the first and second surfaces.
The embodiments directed at different aperture configurations are advantageous in that they allow an air flow to be collected in a first location, say over the OD of the disk, to be redirected to a second location that is not directly over the first location, such as the straight segment of the ramp. These embodiments also allow the air flow out of the apertures to be shaped and otherwise manipulated, for example by providing nozzles to increase the speed of the air flow. Such variations provide greater lift to a tab over some regions of the ramp than over other regions. A properly shaped aperture can reduce turbulence and thus reduce resistance to the flow of air.
More embodiments are directed at ramp systems for loading and unloading at least two sliders. Such an embodiment comprises a body having a first portion and a second portion where each portion is a ramp as described above, and the first portion is proximate to a first surface of a disk and the second portion is proximate to a second surface of the disk. The two portions, taken together, provide the body of the ramp system. The ramp system can be positioned around the OD of the disk. This design is desirable as disk drives typically are configured to be able to utilize both surfaces of a magnetic disk by employing a separate slider for each.
Further embodiments are directed to disk drives for storing and retrieving magnetic data comprising a housing containing a rotatable magnetic disk, an actuator configured to pivot a load beam proximate to a surface of the disk, a slider and a tab each attached to the load beam, the tab extending the load beam in a first direction, and a ramp as described above. The ramp is situated such that the tab engages a sloped segment of the ramp as the load beam is pivoted to an outside diameter of the surface of the disk. Additional embodiments of the disk drive are directed to variations of the tab, and specifically to the surface of the tab that faces the ramp. This surface may have a non-planar component, for example, it can be concave or have an aerodynamic shape to help it glide on the air bearing. Shaping the surface of the tab can be an advantage in that it allows the tab to experience a greater lifting force from the air flow provided by the apertures beneath it.
Lastly, embodiments are directed to methods for loading and unloading a slider. Both methods include providing a rotatable magnetic disk disposed within a housing, providing an actuator disposed within the housing and configured to pivot a load beam proximate to a surface of the disk, providing a slider and a tab attached to the load beam wherein the tab extends the load beam in a first direction, and providing a ramp as described above. The method of loading the slider further includes rotating the magnetic disk to provide an air flow through the plurality of apertures, pivoting the load beam while the air flow through the apertures provides a lifting force to the tab as it moves with respect to the ramp from a straight segment to a sloped segment, and finally flying the slider such that the tab disengages from the ramp.
The method of unloading the slider further includes flying the slider over the disk, pivoting the load beam such that the tab engages a sloped segment of the ramp as the load beam is pivoted to an outside diameter of the disk, moving the tab over the sloped segment and onto the straight segment of the ramp, and reducing the rotation of the disk to reduce the flow of air through the apertures to allow the tab to be supported on the straight segment of the ramp. Further embodiments of both methods include supporting the tab on an air bearing while it is moving relative to the ramp. Other embodiments of both methods are directed to providing an amount of lift to the tab that is not sufficient to raise the tab off of the ramp, but is sufficient to lower the contact force between the tab and the ramp.
These and other advantages of the present invention will become apparent to those skilled in the art upon a reading of the following descriptions of the invention and a study of the several figures of the drawings.